Method, processing unit and surveying instrument for improved tracking of a target

ABSTRACT

A method implemented in a processing unit controlling a surveying instrument is provided. The method comprises obtaining a first set of data from optical tracking of a target with the surveying instrument, and identifying from the first set of data a dependence over time of at least one parameter representative of movements of the target. The method further comprises receiving a second set of data from a sensor unit via a communication channel, the second set of data including information about the at least one parameter over time, and determining whether a movement pattern for the optically tracked target as defined by the dependence over time of the at least one parameter is the same as, or deviates by a predetermined interval from, a movement pattern as defined by the dependence over time of the at least one parameter obtained from the second set of data.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International ApplicationNo. PCT/EP2017/065296, filed Jun. 21, 2017, the contents of which areincorporated herein by reference in their entirety for all purposes.

TECHNICAL FIELD

The present disclosure generally relates to the field of surveying. Inparticular, the present disclosure relates to surveying instrumentsconfigured to track a target and to measure a direction and/or distanceto the target.

BACKGROUND

In the field of surveying there are surveying instruments capable oftracking a moving target. However, targets may be lost during tracking,and due to the surveying instruments' narrow line of sight, finding themagain may be very difficult. This often means manual intervention andre-targeting, which may be time consuming.

Another problem in the present field is to ensure that the target beingtracked is the correct one. In a surveying environment with potentiallya multitude of possible targets and other objects to track, it may behard to verify that the target being tracked is the correct target totrack, and not another target that happened to be caught in the line ofsight of the surveying instrument.

Therefore, a challenge in the present technical field is to provide asurveying instrument with improved tracking of a moving target.

SUMMARY

An object of the present disclosure is therefore to mitigate some of thedrawbacks described above. To achieve this, a method implemented in aprocessing unit controlling a surveying instrument, a processing unitand a surveying instrument as defined in the independent claims areprovided. Further embodiments are defined in the dependent claims.

According to an aspect, a method implemented in a processing unitcontrolling a surveying instrument is provided. The method comprisesobtaining a first set of data from optical tracking of a target with thesurveying instrument, and identifying from the first set of data adependence over time of at least one parameter representative ofmovements of the target. The method further comprises receiving a secondset of data from a sensor unit via a communication channel, the secondset of data including information about the at least one parameter overtime, and determining whether a movement pattern for the opticallytracked target as defined by the dependence over time of the at leastone parameter is the same as, or deviates by a predetermined intervalfrom, a movement pattern as defined by the dependence over time of theat least one parameter obtained from the second set of data.

With this method, the processing unit controlling the surveyinginstrument may receive, and use, more information than before, and maythereby improve the optical tracking of a target. The movementpattern(s) determined from the two datasets may be used to ensure thatthe optical tracking is correctly performed and may be used for ensuringthe identity of the target so that the correct target is opticallytracked.

It has been realized that using data from a sensor unit in combinationwith the data collected by the surveying instrument via optical trackingmay be used to improve the target tracking in general. By, for example,obtaining the data collected by the surveying instrument and the datafrom the sensor unit over time and comparing them, conclusions about thetarget's identity, its rotation, or other conclusions that may improvethe tracking by the surveying instrument may be drawn. Using anotherindependent set of measurement data, such as the second set of data fromthe sensor unit, may help in verifying the accuracy of the opticallytracked data. The use of the two different sets of measurement data maybe used to make the surveying and tracking of targets more automated.Further implementations will be exemplified in the followingembodiments.

The target may be any type of target suitable for optical tracking. Forexample, a target comprising a prism to reflect light transmitted fromthe surveying instrument may be used, but also other types of targetsmay be used.

The surveying instrument may be a geodetic surveying instrument, oranother surveying instrument suitable for optical tracking of a target,i.e. capable of tracking the target as it moves.

It will be appreciated that “determining whether a movement pattern forthe optically tracked target as defined by the dependence over time ofsaid at least one parameter is the same as, or deviates by apredetermined interval from, a movement pattern as defined by thedependence over time of said at least one parameter obtained from thesecond set of data” may be referred to as that the movement patternsmatch, that the movement patterns are similar or that the targets havethe same, or nearly the same, movement pattern.

It will be appreciated that because of e.g. measurement tolerancesand/or other reasons, the two movement patterns, as determined from thefirst and second set of data, respectively, may not be exactly identicalalthough they originate from the same target (i.e. the target beingoptically tracked is the target to which the sensor unit is attached).For this reason, it may be sufficient to determine that the two movementpatterns only differ by a predetermined interval.

In the present specification, the term “movement pattern” may includethe movements over time of any object, approximated into a pattern thatis comparable to other “movement patterns”. As mentioned above, amovement pattern may be defined as the dependence over time of aparameter representative of the movement(s) of the target.

Further, the term “processing unit” may refer to the “processing unitcontrolling a surveying instrument”. The processing unit may be separatefrom the surveying instrument, or it may be part of the surveyinginstrument. The processing unit may also be referred to as a processoror a processing means.

By the term “movements”, any type of movement is referred to, which mayinclude, but is not limited to, changes in tilt, changes in compassdirection or rotation, changes in position, or the like.

The communication channel may be any type of channel or link used forcommunications, for example a wireless channel or link, such as a radiolink, or another connection suitable for communication between devices.

According to an embodiment, the determining may include comparing thedependence over time of the at least one parameter obtained from thesecond set of data with a representation (or dependence) over time ofthe at least one parameter obtained from the first set of data. Thecomparison may be performed on a point-by-point basis, regressionanalysis, interpolation or by approximating a path in a coordinatesystem. For example, a Kalman filter may be used. Comparing the twodatasets over time may give an accurate picture of the movement patternsof the target as represented by the data.

Different amounts of data may be used for the comparison. For example,the processing unit may use data from a predetermined number of secondsin time, or it may use a predetermined number of data points. As theremight be some difference in time between the two data sets, thecomparison may comprise adjusting for differences in time between thefirst and the second data set. Further, there might be a rotation of thetarget in relation to the surveying device which the processing unit mayadjust for before determining if the movement patterns match.

In an embodiment, the method may further comprise determining that thesecond set of data originates from a sensor unit attached at the target(being optically tracked) if the movement pattern for the opticallytracked target is the same as, or deviates by a predetermined amplitude(or interval) from, the movement pattern obtained from the second set ofdata, and continuing optical tracking of the target. Such an amplitude(or interval) may, for example, be at least 120% or 130% of the combinedaccuracy of the sensor unit and of the surveying instrument. Thecombined accuracy is the maximum expected measurement error by thesensor unit and the surveying instrument. For example, if the combinedaccuracy of the sensor unit and of the surveying instrument is +−1%, anamplitude or interval may be a difference within 1.2%. Having thepredetermined amplitude or interval larger than the expected error inmeasurements allows for a more accurate determination that the movementpatterns are the same.

The processing unit may use the received data to verify that the targetbeing optically tracked is the correct one and to continue tracking thetarget when it is determined to be the correct one. This may beadvantageous, for example, when there are multiple potential targets inthe area, or when the target is within an area where there areobstructions for the optical tracking. Instead of, for example,verifying the target's identity manually every time the tracking isresumed, the processing unit may verify it automatically with the datareceived.

According to an embodiment, the method may comprise determining that thesecond set of data does not originate from a sensor unit attached at thetarget being optically tracked if the movement pattern for the target isoutside of a predetermined amplitude or interval of the movement patternobtained from the second set of data. The method may further comprisestopping optical tracking of the target. The processing unit may wait apredetermined amount of time, a predetermined number of measurements, oruntil there is enough data to determine within a predeterminedconfidence interval that the second set of data does not originate froma sensor unit attached at the target being optically tracked, beforestopping optical tracking of the target. The processing unit maydetermine that the target being optically tracked is not the correcttarget, and in response stop tracking the target. Stopping tracking ofan incorrect target may lead to less faulty tracked data. Thedetermination further gives the possibility to early realize that thesurveying instrument is tracking an incorrect target, and to correctthat before time and/or resources may have been wasted.

The method may further comprise initiating a search for the target towhich the sensor unit is attached. The initiation may comprise opticallysearching for a new target, and once a new target is found, using themethod as described above to verify if the target is the correct one. Ifnot, the surveying instrument may initiate another search for thetarget. The search may be initiated automatically when the tracking hasbeen stopped after it has been determined that the target was not thecorrect one. The search may originate from the last known position ofthe correct target, if one is known.

It will be appreciated that a target may comprise a geodetic pole (orrod) and an optical element arranged on the geodetic pole. The geodeticpole may be telescopic and a distance between the sensor unit and theoptical element of the target along the geodetic pole may be input tothe processing unit as a configuration step. In the following, thedistance input to the processing unit may be referred to as a configureddistance. In some embodiments, the sensor unit may be arranged at afixed part of the geodetic pole while the optical element may bearranged at a telescopic (or extendable) part of the geodetic pole. Thedistance between the sensor unit and the optical element may thereforevary from time to time or between different measurements. An operator oruser may enter via a user interface the distance between the sensor unitand the optical element.

In the case of a passive target, the optical element may for example bea prism or a mirror or, more generally, an optically reflecting elementto be used for the purpose of optical tracking. In the case of an activetarget, the optical element may be a light source which then may also beused for the purpose of optical tracking.

If the sensor unit and the optical element are not positioned at thesame position along the geodetic pole, a movement pattern obtained fromthe first set of data (i.e. obtained by optical tracking via the opticalelement) may not be identical to a movement pattern obtained from thesecond set of data (i.e. obtained by the data sent from the sensorunit). However, the movement pattern obtained by the first set of data(i.e. by optical tracking) may be corrected based on the distance, asconfigured, between the sensor unit and the optical element. If thedistance is correctly configured, the corrected movement patternobtained from the first set of data will be equivalent, or at leastresemble, the movement pattern obtained from the second set of data andthe processing unit may be configured to determine that the sensor unit(from which the second set of data is received) is arranged at theoptically tracked target. The surveying instrument may then continue theoptical tracking of the target. In the above examples, it will beappreciated that, instead of the movement pattern obtained from thefirst set of data, the movement pattern obtained from the second set ofdata may be corrected.

According to an embodiment, the target may include a geodetic pole andan optical element for optical tracking, and the method may comprise astep of determining whether, at least based on a configured distancebetween the optical element and the sensor unit along the geodetic pole,a movement pattern obtained by the first set of data (for the opticallytracked target) matches a movement pattern obtained by the second set ofdata. As a result, the processing unit may cause the surveyinginstrument to continue optical tracking of the target.

In the present embodiments, the distance between the optical element andthe sensor unit arranged on the target may be accounted for, therebydecreasing the risk for false determinations that the tracking should bestopped.

According to an embodiment, the method may further comprise, if it hasbeen determined that the movement patterns obtained by the first andsecond sets of data do not match based on the configured distancebetween the sensor unit and the optical element along the geodetic poleof the target, determining whether the movement pattern for theoptically tracked data matches the movement pattern obtained from thesecond set of data using another distance between the sensor unit andthe optical element of the target along the geodetic pole. The methodmay then further comprise a step of sending an alert indicating that thedistance between the sensor unit and the optical element has not beencorrectly configured.

As mentioned above, the surveying instrument may continue opticaltracking of the target. However, if on receipt of the alert, it isdetermined that the distance has in fact been correctly configured, theprocessing unit (or an action of the operator) may cause the opticaltracking to be stopped.

In the above embodiments, it will be appreciated that an operator oruser may have configured a distance a as the expected distance betweenthe sensor unit and the optical element of the target. If is notdetermined that the movement pattern for the optically tracked target isthe same as, or deviates by a predetermined amplitude (or interval)from, the movement pattern obtained from the second set of data, basedon the distance a, there may be a distance d for which it may bedetermined that the movement patterns match. If there is such a distanced, an alert may be sent to indicate that the distance may be incorrectlyconfigured.

By sending an alert that the target is incorrectly configured, measureerrors may be avoided or at least reduced. In this embodiment, a changein distance between the sensor unit and the optical element of thetarget used for optical tracking may be detected. This may be the resultof a change of the telescopic arrangement of the geodetic pole such thatthe distance between the prism or other optical component used foroptical tracking and the sensor unit has changed.

Once the correct target is found and identified, the surveyinginstrument may start optical tracking of the target. This may bebeneficial since the need for manual intervention is reduced, or eveneliminated. Indeed, the surveying instrument may by itself determinethat the target being optically tracked is not the correct one, and inresponse to that information, initiate a search for the correct targetand when found, optically track the target. This may increase theautomation of surveying and tracking targets, and it may further reduceboth the errors and/or the manual work needed, since the processing unitmay initiate the search for the correct target automatically.

According to an embodiment, the method may comprise determining anorientation of the target in relation to the surveying instrument if themovement pattern for the optically tracked target is the same as, ordeviates by a predetermined amplitude or interval from, the movementpattern obtained from the second set of data. A target may be rotated incomparison to the surveying instrument, meaning, for example, that thefront of the target is not facing the same direction as the front of thesurveying instrument. The rotation may affect the optical tracking andthe direction of the sensor unit data. For example, the target'srotation may affect the amount of light that is reflected, or thedirection of the reflected light. Further, determining the orientationof the target together with knowledge of the at least one parameter mayimprove prediction of a future position of the target. The processingunit determining the rotation of the target in comparison to thesurveying instrument (i.e. determining the orientation of the target)may therefore improve optical tracking of the target. Further, using therotation when determining a movement pattern and when comparing the datasets may lead to less computing needed. The determined rotation may alsobe used to rotate the target in a more advantageous way by an operator,if any.

The rotation estimation may be used by the processing unit to resetvelocity- and position drift.

The method may further comprise determining in a coordinate system ofthe surveying instrument a first path of the optically tracked targetbased on the first set of data, determining in the coordinate system asecond path based on the second set of data, comparing the two paths todetermine an angle between the first path and the second path, anddetermining the rotation of the target in relation to the surveyinginstrument based on the comparison (and in particular based on theangle).

The comparison may also be performed by determining the first path basedon the first set of data in a first coordinate system, determining thesecond path based on the second set of data in a second coordinatesystem, and determining, if the movement pattern of the first and seconddata sets are the same or nearly the same, the rotation between the twocoordinate systems. Based on the rotation between the first and secondcoordinate systems an estimation of the rotation of the target inrelation to the surveying instrument may be obtained.

According to an embodiment, the second set of data includes at least oneof data from an accelerometer, data from a gyroscope, compass data, datafrom a barometric altimeter, or data from an image based motion sensor.The processing unit may use such information for improving tracking ashaving this information provides data representative of the target'smovements.

According to the present embodiment, the sensor unit attached at thetarget may for example be an image based motion sensor, i.e. the dataare obtained by image based motion sensing, such that the second set ofdata includes data from such an image based motion sensor. The imagebased motion sensor may be a video camera for video navigation (or fornavigation purposes) and the image based motion sensor (or video camera)is oriented towards the ground (i.e. the field of view of the videocamera is directed towards the ground) such that it provides real timemeasurements of movements.

The image based motion sensor may detect movements in six dimensions inthe sense that it may detect three positions (along three coordinateaxis of a Cartesian coordinate system) and three rotations (around thethree coordinate axis of the Cartesian coordinate system).

According to an embodiment, the at least one parameter representative ofmovements over time of the target includes acceleration, velocity,position, orientation, pressure or temperature. Determining themovements over time may facilitate the comparison of the two datasets.Different types of data may be received from the sensor unit, asdescribed above. Further, different parameters may be suitable dependingon what data is received from the sensor unit to reduce the amount ofprocessing needed.

According to an embodiment, the receiving of the second set of data maycomprise establishing a communication channel between the processingunit and the surveying unit. For establishing a communication channel,the sensor unit sending the data and/or the target to which the datacorresponds may be identified, and the data may thus be sent with lowrisk of being confused with other targets' data. When a communicationchannel is established, the processing unit and the sensor unit maycommunicate and the sensor unit may send the data indicating movementsof the target. Further, with this step, the surveying instrumentestablishes a communication channel with the target which it is supposedto optically track.

The establishing of the communication channel may include using apre-determined frequency. The sensor unit and the processing unit may beconfigured to communicate using a predetermined frequency to facilitatecommunication and recognition of the second set of data by theprocessing unit. In some implementations, the sensor unit associatedwith a specific target and the processing unit may communicate via adedicated frequency, i.e. a frequency unique for this specific target,such that other targets (or rather other sensor units associated withthose targets) communicate using other (different) dedicatedfrequencies.

In an embodiment, the second set of data may comprise an identifier forestablishing communication via the communication channel between thesurveying instrument and the target. This identifier may be used toensure that the second set of data originates from a sensor unitattached to, or associated with, the correct target to be tracked.

In an embodiment, the at least one parameter may include positions ofthe target over time in a coordinate system. The coordinate system maybe any type of coordinate system and representation thereof. The datamay be cleaned before using it for analysis, for example byapproximating, interpolating or determining a movement pattern asindicated by a data set. A movement pattern may be determined for thefirst set of data, and another movement pattern may be determined forthe second set of data.

According to an embodiment, the processing unit may be part of thesurveying instrument. In other words, the processing unit may beintegrated in the surveying instrument. The sensor unit associated withthe target can then be configured to communicate with the surveyinginstrument.

It will also be appreciated that the sensor unit may have one sensitivepart attached to the target for detecting the value of the parameterrepresentative of the target's movements. However, the partcommunicating with the processing unit may be located elsewhere as longas it has obtained the value of the parameter, as measured by thesensitive part.

In an embodiment, the optical tracking may comprise transmitting atransmit light signal toward the target at an emission time, receiving,at a receive time, a return light signal from reflection of the transmitlight signal against the target, and determining a direction and/or aposition of the target based on at least the emission time and thereceive time.

According to one aspect, a processing unit is provided. The processingunit is configured to operate in accordance with a method as defined inany of the previous embodiments.

According to one aspect, a surveying instrument is provided. Thesurveying instrument may comprise a processing unit, as defined in anyone of the embodiments described above.

In one embodiment, the surveying instrument may comprise a transceiverconfigured to communicate with a sensor unit.

In one embodiment, the surveying instrument may comprise a center unithaving an instrument optical axis, the center unit being mounted on analidade for rotation about a first axis and on a base for rotation abouta second axis.

It is noted that embodiments of the invention relate to all possiblecombinations of features recited in the claims. Further, it will beappreciated that the various embodiments described for the method areall combinable with the processing unit and/or surveying device asdefined in accordance with the other aspects of the present invention,and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplifying embodiments will be described below with reference to theaccompanying drawings, in which:

FIG. 1a illustrates a surveying instrument and FIG. 1b illustrates atarget with a sensor unit attached to it;

FIG. 2 is a block diagram of a surveying instrument, a processing unit,a target and a sensor unit in a surveying system according toembodiments of the present disclosure;

FIGS. 3a-3c provide a schematic view of a rotation of a target inrelation to a surveying instrument, and a representation of movements ofa target as measured by a sensor unit and by a surveying instrument;

FIGS. 4a-e shows a schematic view of a surveying instrument trackingmultiple targets, and a representation of movements of a target from asurveying instrument and multiple sensor units, respectively;

FIGS. 5-8 show overviews of one or more embodiments of a methodimplemented in a processing unit.

In the drawings, like reference numerals will be used for like elementsunless stated otherwise. Unless explicitly stated to the contrary, thedrawings show only such elements that are necessary to illustrate theexample embodiments, while other elements, in the interest of clarity,may be omitted or merely suggested. As illustrated in the figures, thesizes of elements and regions may be exaggerated for illustrativepurposes and, thus, are provided to illustrate the general structures ofthe embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS

Exemplifying embodiments will now be described more fully hereinafterwith reference to the accompanying drawings. The drawings show currentlypreferred embodiments, but the invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided forthoroughness and completeness, and fully convey the scope of the presentdisclosure to the skilled person.

FIG. 1A schematically illustrates a surveying instrument 100 inaccordance with some embodiments. The surveying instrument 100 mayinclude a center unit 105, such as a telescope assembly, having aninstrument optical axis 110. The telescope assembly or center unit 105is mounted for rotation about two axes: on a trunnion of an alidade 115for rotation about a first (trunnion) axis 120, and on a base 125 forrotation about a second (azimuthal) axis 130. The surveying instrument100 may for example be a geodetic instrument, such as a total station, ascanner or a theodolite, and is configured to carry out at least partsof one or more methods as will be described later herein.

The surveying instrument 100 may be configured to measure a distance toa target, measure a direction to the target and/or measure a position ofthe target. The surveying instrument 100 may be configured to performtracking of the target. The center unit 105 may be configured to track,determine the distance to, or determine a position of a target byemitting a tracking light signal toward a target and receives a trackingreturn signal, if any, from the target. The center unit 105 may beconfigured to maintain the optical axis 110 of the center unit 105 aimedtoward the target as the target moves.

FIG. 1B illustrates a target 140 that may have a sensor unit 150attached to it. The target 140 may comprise a prism or another opticalelement such as a mirror 145 configured to reflect light. The target 140is configured to carry out at least parts of one or more methods as willbe described later herein.

The surveying instrument 100 may comprise a transceiver configured tocommunicate wirelessly with the sensor unit 150.

The target may, in some examples, comprise a telescopic rod ortelescopic geodetic pole. The rod or pole may comprise an upperextendable portion and a lower non-extendable, i. e. fixed, portion. Theprism or other optical element, such as a mirror, may be arranged on theextendable portion of the rod, while the sensor unit may be arranged onthe fixed part of the rod. With targets comprising a telescopic rod, thelength of the rod may need to be configured in order to correctlycalculate the position of the target.

If the target has a sensor unit, the target 140 may include also abattery (not illustrated) to power the sensor unit 150, although it isenvisaged that power may be provided to the sensor unit 150 also from anexternal source through a wire, solar energy or the like. If, forexample, the target 140 is mounted on a vehicle or other structure,power may be provided to the sensor unit 150 from this vehicle or otherstructure. Alternatively, a battery may be included in the sensor unit150 itself.

The sensor unit 150 is configured to detect one or more parametersrepresentative of a movement of the target 140. The sensor unit 150 maybe configured to collect and transmit data including acceleration,velocity, position, orientation, pressure or temperature of the target140. The sensor unit 150 may further comprise a transceiver (not shown)to wirelessly communicate with the surveying instrument 100 or aprocessing unit associated with the surveying instrument. The sensorunit 150 may be attached to the target 140. The sensor unit 150 isconfigured to carry out at least parts of one or more methods as will bedescribed later herein.

FIG. 2 is an overview of a surveying system comprising a surveyinginstrument 100 (such as e.g. the surveying instrument described withreference to FIG. 1A), a sensor unit 150 attached to a target 140 and aprocessing unit 160. The processing unit 160 may control the surveyinginstrument 100 or the processing unit 160 may provide information toanother processing unit controlling the surveying instrument 100. Theprocessing unit 160 is configured to carry out at least parts of one ormore methods as will be described later herein.

The surveying instrument 100 may transmit an optical signal 170 towardsthe target 140 and the target 140 may reflect the optical signal 170.The reflected signal 172 may be received by the surveying instrument100, and it may be used for determining a distance to the target 140, adirection to the target 140, and/or a position of the target 140. Thedistance to the target 140 may for example be determined using atime-of-flight method based on an emission time at which the opticalsignal 170 is transmitted from the surveying instrument 100 to thetarget 140 and a receive time at which the reflected signal 172 isreceived at the target 140. In other words, the surveying instrument 100may optically track the target 140.

The processing unit 160 may receive data from the sensor unit 150attached to the target 140, and from the surveying instrument 100. Thedata received from the surveying instrument 100 may be a first set ofdata obtained by optical tracking of the target 140, as described above.The data received from the sensor unit 150 may be a second set of dataindicating a movement of the target 140.

The data received from the sensor unit 150 may relate to a specificparameter over time, indicating a movement of a target, or it may be rawmeasurement data. The processing unit 160 may process the data andextract the parameter to obtain the dependence over time of theparameter and thereby determine a movement pattern based on the secondset of data.

Parameters indicating movements of the target may be, but is not limitedto, acceleration, velocity, position, and/or orientation.

In particular, the processing unit may receive data from the sensor unitover a wireless communication channel or link. The processing unit mayidentify the sensor unit from which the data originates based on, butnot limited to, the frequency used to transmit the data was, or anidentifier sent together with the data. The frequency may be apredetermined frequency. The identifier may be any type of data that theprocessing unit may identify the sensor unit, or rather the target towhich the sensor unit is attached, with.

The receiving of the second set of data may comprise receiving anidentifier for establishing communication via the communication channelbetween the surveying instrument and the target.

Still referring to the exemplifying surveying system described withreference to FIG. 2, examples of movement patterns and data aredescribed in the following with reference to FIGS. 3A-3C.

FIG. 3A is an overview of a target 140 and a surveying instrument 100.The surveying instrument may have a forward direction y_(Sl) and a sidedirection x_(Sl). The target may have a front direction y_(T) and a sidedirection x_(T). The target may be rotated in relation to the surveyinginstrument with an angle α.

FIGS. 3B and 3C show example data representative of the movements basedon data from a sensor unit attached to the target 140 and the movementsof the target 140 as determined by a surveying instrument 100,respectively.

The representation f₁ in FIG. 3C is an illustration of example data sentfrom a sensor unit 150 attached to the target 140. The representation f₂in FIG. 3C is an illustration of example data that may be obtained bythe surveying instrument 100 via optical tracking. From data obtained byoptical tracking a processing unit may determine a dependence over timeof a parameter, and thereby determine a movement pattern.

FIG. 3B shows a representation f₁ of the target's movements, or movementpattern, over time as represented by a parameter p over time t, asmeasured by a sensor unit attached to the target 140.

FIG. 3C shows a representation f₂ of the target's movements, or movementpattern, over time as represented by a parameter p over time t, asoptically measured by the surveying instrument. The data may be obtainedduring optical tracking, for example, by determining the position of,distance to or direction of a target.

The processing unit 160 may receive the two sets of data, either the rawmeasurement data itself or a representation f as, for example, shown inFIGS. 3B or 3C. If there is no representation already, the processingunit 160 may analyze the data and extract a representation of thetarget's movements over time with at least one parameter. The processingunit 160 may do a regression analysis or an interpolation of the data.If the data sets have the same parameter over time the processing unit160 may compare them without extracting another parameter over timefirst. The processing unit 160 may extract a parameter only from one ofthe data sets if that parameter is already represented in the other dataset.

The processing unit 160 may further compare the two representations overtime and determine if they have the same movement pattern. Theprocessing unit 160 may determine that the two data sets indicate thesame movement pattern if they are within a predetermined interval, andthe processing unit 160 may, correspondingly, determine that the twodata sets do not indicate the same movement pattern if they are outsideof the predetermined interval or deviation. Such an interval ordeviation may, for example, be 120%, 130% or more of the combinedaccuracy of the sensors.

The processing unit 160 may compare the movements over time in differentways, one example is by comparing on a point-by-point basis. Anotherexample is by comparing approximated functions or paths.

As an illustrative example only, the processing unit 160 may receivedata from the sensor unit 150 indicating the target's acceleration atdifferent points in time. The processing unit may also receive opticaltracking data comprising a target's position at different points intime. The processing unit 160 may process the optical tracking data andextract the target's acceleration at different points in time. Finally,the processing unit 160 may compare the two data sets point by point intime and determine if the acceleration in each point in time are withina predetermined interval from each other.

Once the processing unit 160 has determined that the two datasetsprovide the same, or nearly the same, movement pattern, a rotation ofthe target 140 in relation to the surveying instrument 100 may bedetermined. The angle of the rotation of the target 140 in relation tothe surveying instrument 100 may correspond to the angle between the tworepresentations of movements over time f₁ and f₂ in a coordinate system.

In FIGS. 3B-3C the coordinate system is represented by a two-dimensionalcoordinate system, but also other coordinate systems may be used, forexample a three-dimensional coordinate system. The coordinates may be aparameter p and time t. Different coordinate systems are possible, forexample Cartesian or polar coordinate systems.

The processing unit 160 may also compensate for differences in timebetween the data received from the sensor unit 150 and the data fromoptical tracking of the target 140. The sensor unit 150 may have onetimestamp which may differ from the timestamp of the data obtained fromthe optical tracking.

In response to determining if the movement pattern f₁ as determined fromthe data received from the sensor unit data has the same movementpattern or is within a predetermined interval from a movement pattern f₂as determined by the optically tracked data, the surveying instrument100 may continue tracking the target 140 having the matching movementpattern.

If it has been determined that the movement pattern of an opticallytracked target 140 does not match the movement pattern of the data froma sensor unit 150, the tracking of the target 140 may be stopped. Thetracking may be continued for some more time after the determination hasbeen made. The tracking may be continued until there is enough data todetermine within a predetermined confidence interval that the movementpattern of the optically tracked target does not match the pattern ofthe data from the sensor unit 150.

The processing unit 160 may determine that the two datasets have thesame movement pattern based on a configured distance, along the rod ofthe target 140, between a sensor unit 150 attached to the target 140 andthe optical element 145. This means in other words that, based on adistance as configured to be the (expected) distance between the sensorunit 150 and the optical element 145 along the geodetic pole, themovement pattern obtained from either one of the first or second sets ofdata may be corrected and the corrected movement pattern may be comparedwith the other movement pattern to check whether they match. If it isdetermined that the movement patterns do not match based on theconfigured distance, the processing unit 160 may determine a distancefor which the movement patterns match.

If the processing unit does not find any distance for which one of thetwo movement patters may be corrected in order to match, the opticaltracking may be stopped.

However, if it is determined that there is a distance for which the twomovement patterns can match, then it could be that the distance betweenthe sensor unit and the optical element along the geodetic pole of thetarget 140 has not been configured correctly. The surveying instrument100 may then continue tracking the target 140.

If it has been determined that the distance along the rod of the target140 between the sensor unit 150 and the optical element 145 has not beenconfigured correctly, an alert may be sent (e.g. to the operator/uservia a user interface or other means). The processing unit 160 may sendthe alert.

If the tracking has been stopped, the surveying instrument 100 mayinitiate a search for a target to optically track, and use any steps ormethods as described herein.

It will be appreciated that a processing unit 160 may communicate withseveral sensor units.

With reference to FIG. 4, a method implemented in a processing unit 160for searching for a (lost or not yet tracked) target is described.

A surveying instrument 100 may lose track of a target and initiate asearch to find it again. Alternatively, the surveying instrument 100 mayinitiate tracking of a target. However, there might be several potentialtargets in the environment.

FIG. 4A is an overview of a surveying instrument 100 identifyingmultiple potential targets 140Aa, 140B, 140C in an environment viaoptical tracking. The processing unit 160 may obtain optical trackingdata for all of the targets 110A, 110B, 110C. The processing unit 160may also receive data from a sensor unit 150 attached to the correcttarget (i.e. the target that the surveying instrument 100 is supposed totrack). FIG. 4B shows example data from a sensor unit attached to thecorrect target. FIGS. 4C, 4D, 4E show example data of the targets 110A,110B, 110C as obtained by optical tracking. The processing unit 160 maycompare the data 4B of the sensor unit 150 with the data represented inFIGS. 4C, 4D, 4E of the targets 110A, 110B, 110C, respectively, todetermine if any of the data has the same, or nearly the same, movementpattern as the data from the sensor unit 150. In the present example,the processing unit 160 may determine that the movement pattern of thedata represented by 4Cc has the same, or nearly the same, movementpattern, or is within a predetermined interval, of the movement patternof the data 4B obtained from the sensor unit 150. As indicated by FIGS.4B and 4C, the processing unit 160 may have to adjust for time as wellas rotation to improve the comparison of the data.

When it has been determined that the movement pattern of the data shownin FIG. 4C matches the movement pattern in FIG. 4B, it may be furtherdetermined the sensor unit communicating the data of FIG. 4B is attachedto target 140A.

It may be determined that the data shown in FIG. 4B does not originatefrom a sensor unit 150 attached to any of the targets 110B or 110C sincethe movement patterns shown in FIG. 4D and FIG. 4E do not match or arewithin a predetermined interval of the movement pattern shown in FIG.4B.

FIG. 5 is an overview of a method 500 implemented in a processing unit160 controlling a surveying instrument 100.

The method 500 includes a step of obtaining 510 a first set of data. Thefirst set of data may be obtained from the surveying instrument 100.From the data, a representation of movements over time may be determined520. The movements over time may be represented by a specific parameter,as suitable (and as described above).

The method may further comprise a step of receiving 530 a second set ofdata. The second set of data may also include information about thespecific parameter obtained from the first set of data. The second setof data may be received from a sensor unit over a communication channel.

It will be appreciated that the steps 510-520 and 530 may be performedin any order.

The method may further include determining 540 if the movement patternof the first set of data is similar, equal to, or within a predeterminedrange from the second set of data.

If it has been determined that the movement patterns match, it may bedetermined 550 that the second set of data originates from a sensor unitattached to the target from which the first set of data 550 has beenobtained by optical tracking. The tracking may then be continued 560.

FIG. 6 illustrates more steps possible after it has been determined instep 540 that the movement patterns match or deviate by a predeterminedinterval.

For example, a rotation of the target in relation to the surveyinginstrument may be determined 610. The step 610 may comprise sub-steps asin 612-618. It may comprise a sub step 612 of determining, in acoordinate system, a first path of the optically tracked target based onthe first set of data. The coordinate system, as mentioned above, may beany coordinate system for the parameter over time.

The step 610 may further comprise a sub step 614 of determining, whichmay be in the coordinate system as used in sub step 612, a second pathbased on the second set of data.

It will be appreciated that the sub steps 612 and 614 may be performedin any order.

The step 610 may further comprise a sub step 616 of comparing the twopaths, as determined in sub steps 612 and 614, to determine an anglebetween the first path and the second path. The angle may be determined,as suitable, in the coordinate system used.

The step 610 may further comprise a sub step 618 of determining therotation of the target in relation to the surveying instrument based onthe comparison. The determining of the rotation may be based on theangle. In some coordinate systems the angle between the two pathsdirectly correspond to the rotation of the target in relation of thesurveying system.

It will be appreciated that the steps 560 and 550 may be performed inany order.

FIG. 7 is an illustration of steps possible after it has been determinedin step 540 that the movement patterns do not match.

If it has been determined that the movement patterns do not match and/orare not within a predetermined interval from each other in step 540, itmay be determined in step 710 that the second set of data does notoriginate from a sensor unit attached to the target of the first set ofdata. It may also be concluded that the optically tracked target is notthe correct target to track.

The optical tracking of the target may therefore be stopped, step 720.Instead, a search for the target to which the sensor unit is attachedmay be initiated, step 730.

The search may be optically done, or visually, depending on thecapabilities of the surveying instrument. Once a new potential targethas been found, the method 500 may be performed again.

The optical tracking 510 of a target may comprise the step 810 oftransmitting a light signal towards a target at an emission time, thestep 820 of receiving, at a receive time, a return light signal fromreflection of the transmit light signal against the target, and the step830 determining a direction and/or a position of the target based on atleast the emission time and receive time. Different light sources and/ordifferent receivers may be used for determining the direction and theposition of the target. For example, a first light source and a firstreceiver may be used for determining the direction of a target, and asecond light source and a second receiver may be used for determiningthe distance to the target or a position of the target.

A processing unit may be configured to contain instructions that, whenexecuted, causes the processing unit to, by itself and/or by directingother components that are also included, perform one or more steps ormethods according to any embodiments described herein. If a methodinvolves the operation of several devices, such as a surveyinginstrument, a sensor unit and a target, a processing unit for asurveying instrument may be responsible for performing the parts of amethod which involves the device which the processing unit is configuredto control (and possible in which it is located).

The steps of any method disclosed herein do not necessarily have to beperformed in the exact order disclosed, unless explicitly stated to thecontrary.

The person skilled in the art realizes that the present disclosure is byno means limited to the embodiments described above. On the contrary,many modifications and variations are possible within the scope of theappended claims.

Although features and elements are described above in particularcombinations, each feature or element may be used alone without theother features and elements or in various combinations with or withoutother features and elements.

Further, although applications of the surveying instrument and targethave been described with reference to a surveying system, the presentdisclosure may be applicable to any systems or instruments in which atarget or object has to be detected in the vicinity of such a surveyinginstrument.

Additionally, variations to the disclosed embodiments can be understoodand effected by the skilled person in practicing the claimed invention,from a study of the drawings, the disclosure, and the appended claims.In the claims, the word “comprising” does not exclude other elements,and the indefinite article “a” or “an” does not exclude a plurality. Themere fact that certain features are recited in mutually differentdependent claims does not indicate that a combination of these featurescannot be used to advantage.

1. Method implemented in a processing unit controlling a surveyinginstrument, the method comprising: obtaining a first set of data fromoptical tracking of a target with the surveying instrument; identifyingfrom the first set of data a dependence over time of at least oneparameter representative of movements of said target; receiving a secondset of data from a sensor unit via a communication channel, said secondset of data including information about said at least one parameter overtime; determining that the second set of data originates from a sensorunit attached at the target if a movement pattern for the opticallytracked target as defined by the dependence over time of said at leastone parameter is the same as, or deviates by a predetermined intervalfrom, a movement pattern as defined by the dependence over time of saidat least one parameter obtained from the second set of data; andcontinuing optical tracking of said target.
 2. The method of claim 1,wherein the determining includes comparing the dependence over time ofsaid at least one parameter obtained from the second set of data with arepresentation over time of said at least one parameter obtained fromthe first set of data.
 3. (canceled)
 4. The method of claim 1, furthercomprising: determining that the second set of data does not originatefrom a sensor unit attached at the target if the movement pattern forthe target is outside of a predetermined interval of the movementpattern obtained from the second set of data; and stopping opticaltracking of said target.
 5. The method of claim 4, further comprising:initiating a search for the target to which the sensor unit is attached.6. The method of claim 1, wherein the method further comprisesdetermining whether, at least based on a configured distance between anoptical element for optical tracking arranged on a geodetic pole of saidtarget and a sensor unit attached to said target, a movement patternobtained by the first set of data matches a movement pattern obtained bythe second set of data.
 7. The method of claim 6, further comprising:determining, if it has been determined that the movement patternsobtained by the first and second sets of data do not match based on theconfigured distance between the sensor unit attached to said target andthe optical element along the geodetic pole of the target, whether themovement pattern for the optically tracked target matches the movementpattern obtained from the second set of data using another distancebetween the sensor unit and the optical element of the target along thegeodetic pole.
 8. The method of claim 1, further comprising: if themovement pattern for the optically tracked target is the same as, ordeviates by a predetermined interval from, the movement pattern obtainedfrom the second set of data, determining an orientation of the target inrelation to the surveying instrument by: determining in a coordinatesystem of the surveying instrument a first path of the optically trackedtarget based on the first set of data; determining in the coordinatesystem a second path based on the second set of data; comparing the twopaths to determine an angle between the first path and the second path;and determining the rotation of the target in relation to the surveyinginstrument based on said comparison.
 9. (canceled)
 10. The method ofclaim 1, wherein the second set of data includes at least one of datafrom an accelerometer, data from a gyroscope, compass data, data from abarometric altimeter, or data from an image based motion sensor.
 11. Themethod of claim 1, wherein the at least one parameter representative ofmovements over time of the target includes acceleration, velocity,position, orientation, pressure or temperature.
 12. The method of claim1, wherein the receiving of the second set of data comprisesestablishing a communication channel between the processing unit and thesensor unit.
 13. The method of claim 12, wherein the establishingincludes using a pre-determined frequency.
 14. The method of claim 1,wherein the second set of data comprises an identifier for establishingcommunication between the surveying instrument and the target via thecommunication channel.
 15. The method of claim 1, wherein the at leastone parameter includes positions of the target over time in a coordinatesystem.
 16. (canceled)
 17. The method of claim 1, wherein said opticaltracking comprises: transmitting a transmit light signal toward thetarget at an emission time; receiving, at a receive time, a return lightsignal from reflection of the transmit light signal against the target;and determining a direction and/or a position of the target based on atleast the emission time and the receive time.
 18. A processing unit,wherein the processing unit is configured to operate in accordance witha method as defined in claim
 1. 19. A surveying instrument comprising aprocessing unit as defined in claim
 18. 20. The surveying instrument ofclaim 19, comprising a transceiver configured to communicate with asensor unit.
 21. The surveying instrument of claim 19, furthercomprising a center unit having an instrument optical axis, the centerunit being mounted on an alidade for rotation about a first axis and ona base for rotation about a second axis.
 22. Method implemented in aprocessing unit controlling a surveying instrument, the methodcomprising: obtaining a first set of data from optical tracking of atarget with the surveying instrument; identifying from the first set ofdata a dependence over time of at least one parameter representative ofmovements of said target; receiving a second set of data from a sensorunit via a communication channel, said second set of data includinginformation about said at least one parameter over time; determiningwhether a movement pattern for the optically tracked target as definedby the dependence over time of said at least one parameter is the sameas, or deviates by a predetermined interval from, a movement pattern asdefined by the dependence over time of said at least one parameterobtained from the second set of data; and if the movement pattern forthe optically tracked target is the same as, or deviated by apredetermined interval from, the movement pattern obtained from thesecond set of data, determining an orientation of the target in relationto the surveying instrument by: determining in a coordinate system ofthe surveying instrument a first path of the optically tracked targetbased on the first set of data; determining in the coordinate system asecond path based on the second set of data; comparing the two paths todetermine an angle between the first path and the second path; anddetermining the rotation of the target in relation to the surveyinginstrument based on said comparison.
 23. The method of claim 22, whereinthe at least one parameter representative of movements over time of thetarget includes acceleration, velocity, position, orientation, pressureor temperature.